Whether it’s a foal wobbling around a stall for the first time or researchers completing their first preliminary study, small steps are an important part of the horse world. British researchers recently took one such step in the realm of understanding laminitis: While much more work is needed to confirm the theory, researchers have obtained some preliminary evidence suggesting that evaluating blood levels of certain anti-inflammatory markers might indicate a horse is at increased risk of developing laminitis.

Several factors can increase a horse's or pony's risk of developing pasture-associated laminitis (PAL), including pasture composition, time of year, age, gender, being a pony, incidence of previous laminitic episodes, obesity, or abnormal insulin dynamics (such as insulin resistance). Some researchers have found that inflammation is an important component of human metabolic syndrome, a condition that has some similarities with PAL; however, inflammation's role in laminitis remains a mystery. Thus, a team of researchers led by Nicola Menzies-Gow, MA, VetMB, PhD, Dipl. ECEIM, CertEM (Int.med), FHEA, MRCVS, a senior lecturer in equine medicine at Royal Veterinary College, set out to determine if there was any relationship between the levels of key inflammatory markers or pro-inflammatory mediators and laminitis history.

For their study, Menzies-Gow and colleagues looked at 80 native-bred mare and gelding ponies (standing 14.3 hands or less) from Redwings Horse Sanctuary and the Royal Veterinary College at the University of London, England. The team separated the animals into two groups: one including ponies that had suffered from at least one veterinary-diagnosed laminitic episode in the past three years (PL group) and a control group of ponies that had never exhibited clinical signs of laminitis (NL group). All ponies grazed pasture and received hay in the winter months from May 2010 until January 2011. Menzies-Gow said the ponies' grass intake was restricted during the summer via strip grazing "to minimize occurrence of laminitis and help prevent obesity.” The researchers collected a variety of different data on the ponies throughout the study and compared results from the PL group to those from the NL group. Some key findings included:

The ponies' estimated weight, body condition score, and neck crest height and thickness—measured once in late spring and once in winter by at least two different trained assessors—did not differ between the NL and PL groups. All ponies weighed more and had a higher body condition score in the winter compared to late spring, but all ponies' crest height was greater in the spring. The team believed the increase in weight and condition in the winter might have been in part due to an increase in hay consumption compared to restricted access to grass in the summer months. Additionally, they noted that the ponies' thicker winter coats could have confounded the results, as they used weigh tapes rather than calibrated scales.

The team collected blood samples from each pony at the beginning of the study (late spring samples) and again eight months later (winter samples) and evaluated them for various biochemical and inflammatory markers. They found one that appeared to be associated with laminitis status: adiponectin. Adiponectin is a hormone secreted by fat cells that is involved in glucose regulation as well as fat breakdown and inhibits TNF-α—a cytokine that promotes inflammation. Low adiponectin levels are often observed in humans with obesity and metabolic syndrome and, in this study, plasma adiponectin was lower in ponies that had suffered from laminitis previously.

Interestingly, the team noted, in this study laminitic status did not influence ponies' serum insulin, a result that contradicts some previous studies. The ponies' insulin concentrations were, however, affected by the time of year. Average insulin concentrations were much higher in the late spring when ponies were consuming just grass compared to winter levels.

Take-Home Message

The researchers concluded that previous laminitis appeared to be associated with a reduced anti-inflammatory capacity, rather than increased pro-inflammatory activity as hypothesized. They believe it would be valuable to determine if reduced levels of a panel of anti-inflammatory markers could predict if a horse or pony is at increased risk for suffering a laminitic episode.

The team cautioned that for many of the parameters evaluated, it's not known whether the time of day sampled affected the results. Coupled with several other factors—including a known diurnal insulin variation, the fact that the animals weren't fasted, and the length of sampling time—this means the results potentially could be confounded, the researchers said. Further studies are therefore needed to confirm these potentially valuable results.

About the Author

Kristen M. Janicki, a lifelong horsewoman, was born and raised in the suburbs of Chicago. She received her Bachelor of Science degree in Animal Sciences from the attend the University of Illinois at Urbana-Champaign and later attended graduate school at the University of Kentucky, studying under Dr. Laurie Lawrence in the area of Equine Nutrition. Kristen began her current position as a performance horse nutritionist for Mars Horsecare, US, Inc., and Buckeye Nutrition, in 2010. Her job entails evaluating and improving the performance of the sport horse through proper nutrition.

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